1. Field of the Invention
The present invention relates to a guide shoe with a shoe surface on which a traveling chain is guided.
2. Description of the Related Art
A chain guide is conventionally known which is assembled in a timing system in an engine room in an automobile to guide a chain traveling between sprockets to properly maintain chain tension. Such a chain guide includes a guide shoe with a shoe surface and a base member that supports the guide shoe along a guide longitudinal direction.
Various shoe surface aspects of such a guide shoe are well known. For example, in the known aspects, a chain plate end surface is slidably guided along a shoe surface shaped like a flat surface or a chain roller is rolled and guided by a guiding protruding portion formed on the shoe surface.
However, in the former guide shoe, the sliding of the chain plate end surface on the shoe surface disadvantageously causes an increase in chain traveling resistance, promoting sliding friction of the guide shoe. In the latter guide shoe, the chain roller intermittently collides against an upstream end of the guiding protruding portion, and the collision disadvantageously causes noise and increases friction losses.
Thus, in order to solve the above-described problem, the present applicant has proposed a guide shoe in which a shoe surface includes a plate guide surface which is formed on an upstream side of the shoe surface in the shoe longitudinal direction and on which only the chain plate is slidably guided, a guiding protruding portion which is formed on a downstream side of the plate guide surface and on which only the chain roller is guided, and a continuously transitioning protruding portion that smoothly connects the plate guide surface and the guiding protruding portion together such that slidable guiding of the chain plate on the chain plate can be smoothly shifted, by the continuously transitioning protruding portion, to rolling guidance of the chain roller by the guiding protruding portion, with a possible excessive collision between the chain roller and the guiding protruding portion avoided (see Japanese Patent Application Laid-open No. H10-184828).
In the guide shoe described in Japanese Patent Application Laid-open No. H10-184828, the height dimension of the guiding protruding portion from the shoe surface is designed to enable avoidance of contact of the chain plate end surface with the shoe surface when the chain roller is guided by the guiding protruding portion. However, in view of possible wear of the guiding protruding portion, possible dimensional errors in chain components, and the like, the height dimension of the guiding protruding portion needs to be equal to or larger than a design value. As a result, a pitch line of the chain traveling on the guide shoe is disadvantageously significantly shifted upward at the guiding protruding portion.
Thus, the present invention is intended to solve such a problem. An object of the present invention is to provide a guide shoe having a simple structure and suppressing a significant shift in pitch line while reducing friction losses and preventing possible noise.